This invention relates to laryngeal mask airway devices (LMA-devices) which are artificial airway devices permitting spontaneous or artificial ventilation of the lungs of a patient.
LMA-devices are described in UK Patents Nos. 2,111,394 and 2,205,499. Such devices have become accepted items of equipment for rapidly and reliably establishing an unobstructed airway in a patient in emergency situations and in the administration of anaesthetic gases, and have found use in most countries of the world.
The insertion of such a LMA-device into the throat of the patient is, in the great majority of cases an entirely straightforward procedure which can be carried out successfully following readily understandable training. FIG. 1 illustrates a preferable situation for the insertion of an LMA-device into a patient's throat. The inflatable cuff surrounding the bowl of the mask is fully deflated and correctly oriented and aligned for passage through the back of the mouth and into the throat. The semi-rigid bowl of the mask is supported by the anesthetist's hand grasping the flexible airway tube adjacent its junction with the mask in order to gently urge the mask into the patient's throat.
Circumstances do, however, occasionally arise during insertion leading to undesirable positioning of the device and/or undesirable forces being applied to the device and/or to the patient. One of the most common of such circumstances is that the leading end of the device, i.e., the distal end of the fully deflated inflatable cuff formation, becomes folded over on itself presenting the more rigid distal end of the mask to catch the inside the throat and subject the patient to undesirable forces. Alternatively, or additionally, the folded over distal end of the cuff will obstruct correct and full inflation of the cuff thereby obstructing the creation of a full seal around the patient's laryngeal inlet and hence obstructing formation of a full enclosed airway to the patient's lungs. This, in turn, may result in anesthetic gases passing unnecessarily into the patient's oesophagus and in any matter regurgitated through the oesophagus entering the larynx and soiling the patient's trachea and lungs.